Seem to be stuck in a 'loop' of sorts, where the gateway seems to be receiving what looks like (multiple!) requests for id from the node, each time with a different child-sensor-id?? However, (and I might be wrong - is there a legend for the debug outputs avaiable anywhere?) the sensor node doesn't seem to be receiving any messages at all? It seems to be retrying until TSM:FAIL:CNT=7, then waits a bit, and the whole loop starts again.

I tried changing the capacitors on the nRF24L01+ (initially had 4.7uF), ran an additional node on an old Genuino UNO, with a new radio, but stuck with the same 'loop'...

I'm seeing exactly the same with my atmega1284p based sensor, the atmega328p based sensors do get replies from the gateway, FPAR does get a response on my atmega328p sensors.
Maybe this is a timing issue ?

@mfalkvidd Many thanks for the link to the log parser!!
Don't know where the 123 appeared from, must have set it at some point in the endless attempts I have made.
Cleared EEPROM on both gw and node, and the log seems to have changed somewhat. It's now receiving OK response to FPAR, but then no response to ID:REQ.

@GertSanders, I don't know that that's what's happening my end. All three of mine are 328p, however, gw is 3.3v pro mini (8MHz), one of the nodes I tried is 5v pro mini (16MHz), and the other node is the old 5v uno (also 16MHz). I did set them all to 38400. Just to rule something similar out, I've flashed the 5v pro mini with the gw code and ran the node on the uno.

@mfalkvidd That would explain a few things!
I've installed HomeGenie on pi (mainly because it supports C# and I'm not as fluent in C++ or Java), but from what I can see, it's support for MySensors is in beta (though the Controllers comparison page is quite old, so don't know how reliable that info is).
I basically wanted something with a nice GUI that I wouldn't have to spend too much time prettying up (or prettying up in C++ or Java, for that matter ). I'll try connecting the two and have a play with it this weekend.
Thanks again for your help!

I basically wanted something with a nice GUI that I wouldn't have to spend too much time prettying up (or prettying up in C++ or Java, for that matter ). I'll try connecting the two and have a play with it this weekend.

Try Domoticz. You will be able to quickly set it up and it does have a nice GUI

My gateway does not use encryption yet. But I was trying to get some sketches' memory use small enough so that they would work when I switch to encryption. To test this, I enabled MY_SIGNING_SIMPLE_PASSWD encryption on them, and then checked if memory use stayed below 80%.

Then, when I commented out MY_SIGNING_SIMPLE_PASSWD, I expected the node to just reconnect to my non-encrypted network. But it didn't.

When I first noticed that nodes I was building (with old nano's) weren't connecting to Domoticz, I blamed domoticz. And then I started using the 'manual' connection settings. Here's some code from a node:

@alowhum then I think it is related to node id:s. The simple flags does not write to eeprom nor does they read from it. Hence the term "simple". Only the security personalizer does that and I assume you did not run that.

@alowhum one way to check is to run the security personaliser without changing it. It will print the security related contents in eeprom. Then enable the simple flag, run a sketch with it, then re-run the personaliser and see if the eeprom content changed.